1. Field of the Invention
This invention relates to a splitting method for an optical device wafer in which a light emitting layer having a plurality of optical devices is formed by epitaxial growth on a substrate for crystal growth of sapphire or the like.
2. Description of the Related Art
By a fabrication process of an optical device such as a laser diode (LD) or a light emitting diode (LED), an optical device wafer is fabricated in which a light emitting layer (epitaxial layer) having a plurality of optical devices is formed by, for example, epitaxial growth on an upper face of a substrate for crystal growth formed from sapphire, SiC or the like. An optical device such as an LD or an LED is formed in each of regions partitioned by scheduled splitting lines formed like a lattice, and individual optical devices are fabricated by splitting the optical device wafer along the scheduled splitting lines into pieces.
Conventionally, as a method of splitting an optical device wafer along scheduled splitting lines, a method is known in which a pulse laser beam of a wavelength having absorbability by the wafer is irradiated along the scheduled splitting lines to form laser worked grooves and then external force is applied to the laser worked grooves to cut the optical device wafer (refer to, for example, Japanese Patent Laid-Open No. Hei 10-305420). Also another method has been proposed in which the focal point of a pulse laser beam of a wavelength having transmittance through the optical device wafer is adjusted to the inside of the wafer, the pulse laser beam is irradiated to form modification layers along the scheduled splitting lines in the inside of the wafer, and then external force is applied to the scheduled splitting lines along which the strength is reduced by the modification layers to split the optical device wafer (refer to, for example, Japanese Patent Laid-Open No. 2005-86161).
Meanwhile, an optical device chip having a reflective film formed on the reverse surface side thereof in order to enhance the luminance of an optical device is proposed in Japanese Patent Laid-Open No. 10-125956 and Japanese Patent Laid-Open No. Hei 10-308532.